/**
 * @file
 * HTTP client
 */

/*
 * Copyright (c) 2018 Simon Goldschmidt <goldsimon@gmx.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Simon Goldschmidt <goldsimon@gmx.de>
 */

/**
 * @defgroup httpc HTTP client
 * @ingroup apps
 * @todo:
 * - persistent connections
 * - select outgoing http version
 * - optionally follow redirect
 * - check request uri for invalid characters? (e.g. encode spaces)
 * - IPv6 support
 */

#include "lwip/apps/http_client.h"

#include "lwip/altcp_tcp.h"
#include "lwip/dns.h"
#include "lwip/debug.h"
#include "lwip/mem.h"
#include "lwip/altcp_tls.h"
#include "lwip/init.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#if LWIP_TCP && LWIP_CALLBACK_API

/**
 * HTTPC_DEBUG: Enable debugging for HTTP client.
 */
#ifndef HTTPC_DEBUG
#define HTTPC_DEBUG                 LWIP_DBG_OFF
#endif

/** Set this to 1 to keep server name and uri in request state */
#ifndef HTTPC_DEBUG_REQUEST
#define HTTPC_DEBUG_REQUEST         0
#endif

/** This string is passed in the HTTP header as "User-Agent: " */
#ifndef HTTPC_CLIENT_AGENT
#define HTTPC_CLIENT_AGENT "lwIP/" LWIP_VERSION_STRING " (http://savannah.nongnu.org/projects/lwip)"
#endif

/* the various debug levels for this file */
#define HTTPC_DEBUG_TRACE        (HTTPC_DEBUG | LWIP_DBG_TRACE)
#define HTTPC_DEBUG_STATE        (HTTPC_DEBUG | LWIP_DBG_STATE)
#define HTTPC_DEBUG_WARN         (HTTPC_DEBUG | LWIP_DBG_LEVEL_WARNING)
#define HTTPC_DEBUG_WARN_STATE   (HTTPC_DEBUG | LWIP_DBG_LEVEL_WARNING | LWIP_DBG_STATE)
#define HTTPC_DEBUG_SERIOUS      (HTTPC_DEBUG | LWIP_DBG_LEVEL_SERIOUS)

#define HTTPC_POLL_INTERVAL     1
#define HTTPC_POLL_TIMEOUT      30 /* 15 seconds */

#define HTTPC_CONTENT_LEN_INVALID 0xFFFFFFFF

/* GET request basic */
#define HTTPC_REQ_11 "GET %s HTTP/1.1\r\n" /* URI */\
    "User-Agent: %s\r\n" /* User-Agent */ \
    "Accept: */*\r\n" \
    "Connection: Close\r\n" /* we don't support persistent connections, yet */ \
    "\r\n"
#define HTTPC_REQ_11_FORMAT(uri) HTTPC_REQ_11, uri, HTTPC_CLIENT_AGENT

/* GET request with host */
#define HTTPC_REQ_11_HOST "GET %s HTTP/1.1\r\n" /* URI */\
    "User-Agent: %s\r\n" /* User-Agent */ \
    "Accept: */*\r\n" \
    "Host: %s\r\n" /* server name */ \
    "Connection: Close\r\n" /* we don't support persistent connections, yet */ \
    "\r\n"
#define HTTPC_REQ_11_HOST_FORMAT(uri, srv_name) HTTPC_REQ_11_HOST, uri, HTTPC_CLIENT_AGENT, srv_name

/* GET request with proxy */
#define HTTPC_REQ_11_PROXY "GET http://%s%s HTTP/1.1\r\n" /* HOST, URI */\
    "User-Agent: %s\r\n" /* User-Agent */ \
    "Accept: */*\r\n" \
    "Host: %s\r\n" /* server name */ \
    "Connection: Close\r\n" /* we don't support persistent connections, yet */ \
    "\r\n"
#define HTTPC_REQ_11_PROXY_FORMAT(host, uri, srv_name) HTTPC_REQ_11_PROXY, host, uri, HTTPC_CLIENT_AGENT, srv_name

/* GET request with proxy (non-default server port) */
#define HTTPC_REQ_11_PROXY_PORT "GET http://%s:%d%s HTTP/1.1\r\n" /* HOST, host-port, URI */\
    "User-Agent: %s\r\n" /* User-Agent */ \
    "Accept: */*\r\n" \
    "Host: %s\r\n" /* server name */ \
    "Connection: Close\r\n" /* we don't support persistent connections, yet */ \
    "\r\n"
#define HTTPC_REQ_11_PROXY_PORT_FORMAT(host, host_port, uri, srv_name) HTTPC_REQ_11_PROXY_PORT, host, host_port, uri, HTTPC_CLIENT_AGENT, srv_name

typedef enum ehttpc_parse_state {
    HTTPC_PARSE_WAIT_FIRST_LINE = 0,
    HTTPC_PARSE_WAIT_HEADERS,
    HTTPC_PARSE_RX_DATA
} httpc_parse_state_t;

typedef struct _httpc_state {
    struct altcp_pcb* pcb;
    ip_addr_t remote_addr;
    u16_t remote_port;
    int timeout_ticks;
    struct pbuf* request;
    struct pbuf* rx_hdrs;
    u16_t rx_http_version;
    u16_t rx_status;
    altcp_recv_fn recv_fn;
    const httpc_connection_t* conn_settings;
    void* callback_arg;
    u32_t rx_content_len;
    u32_t hdr_content_len;
    httpc_parse_state_t parse_state;
#if HTTPC_DEBUG_REQUEST
    char* server_name;
    char* uri;
#endif
} httpc_state_t;

/** Free http client state and deallocate all resources within */
static err_t
httpc_free_state(httpc_state_t* req)
{
    struct altcp_pcb* tpcb;

    if (req->request != NULL) {
        pbuf_free(req->request);
        req->request = NULL;
    }
    if (req->rx_hdrs != NULL) {
        pbuf_free(req->rx_hdrs);
        req->rx_hdrs = NULL;
    }

    tpcb = req->pcb;
    mem_free(req);
    req = NULL;

    if (tpcb != NULL) {
        err_t r;
        altcp_arg(tpcb, NULL);
        altcp_recv(tpcb, NULL);
        altcp_err(tpcb, NULL);
        altcp_poll(tpcb, NULL, 0);
        altcp_sent(tpcb, NULL);
        r = altcp_close(tpcb);
        if (r != ERR_OK) {
            altcp_abort(tpcb);
            return ERR_ABRT;
        }
    }
    return ERR_OK;
}

/** Close the connection: call finished callback and free the state */
static err_t
httpc_close(httpc_state_t* req, httpc_result_t result, u32_t server_response, err_t err)
{
    if (req != NULL) {
        if (req->conn_settings != NULL) {
            if (req->conn_settings->result_fn != NULL) {
                req->conn_settings->result_fn(req->callback_arg, result, req->rx_content_len, server_response, err);
            }
        }
        return httpc_free_state(req);
    }
    return ERR_OK;
}

/** Parse http header response line 1 */
static err_t
http_parse_response_status(struct pbuf* p, u16_t* http_version, u16_t* http_status, u16_t* http_status_str_offset)
{
    u16_t end1 = pbuf_memfind(p, "\r\n", 2, 0);
    if (end1 != 0xFFFF) {
        /* get parts of first line */
        u16_t space1, space2;
        space1 = pbuf_memfind(p, " ", 1, 0);
        if (space1 != 0xFFFF) {
            if ((pbuf_memcmp(p, 0, "HTTP/", 5) == 0)  && (pbuf_get_at(p, 6) == '.')) {
                char status_num[10];
                size_t status_num_len;
                /* parse http version */
                u16_t version = pbuf_get_at(p, 5) - '0';
                version <<= 8;
                version |= pbuf_get_at(p, 7) - '0';
                *http_version = version;

                /* parse http status number */
                space2 = pbuf_memfind(p, " ", 1, space1 + 1);
                if (space2 != 0xFFFF) {
                    *http_status_str_offset = space2 + 1;
                    status_num_len = space2 - space1 - 1;
                }
                else {
                    status_num_len = end1 - space1 - 1;
                }
                memset(status_num, 0, sizeof(status_num));
                if (pbuf_copy_partial(p, status_num, (u16_t)status_num_len, space1 + 1) == status_num_len) {
                    int status = atoi(status_num);
                    if ((status > 0) && (status <= 0xFFFF)) {
                        *http_status = (u16_t)status;
                        return ERR_OK;
                    }
                }
            }
        }
    }
    return ERR_VAL;
}

/** Wait for all headers to be received, return its length and content-length (if available) */
static err_t
http_wait_headers(struct pbuf* p, u32_t* content_length, u16_t* total_header_len)
{
    u16_t end1 = pbuf_memfind(p, "\r\n\r\n", 4, 0);
    if (end1 < (0xFFFF - 2)) {
        /* all headers received */
        /* check if we have a content length (@todo: case insensitive?) */
        u16_t content_len_hdr;
        *content_length = HTTPC_CONTENT_LEN_INVALID;
        *total_header_len = end1 + 4;

        content_len_hdr = pbuf_memfind(p, "Content-Length: ", 16, 0);
        if (content_len_hdr != 0xFFFF) {
            u16_t content_len_line_end = pbuf_memfind(p, "\r\n", 2, content_len_hdr);
            if (content_len_line_end != 0xFFFF) {
                char content_len_num[16];
                u16_t content_len_num_len = (u16_t)(content_len_line_end - content_len_hdr - 16);
                memset(content_len_num, 0, sizeof(content_len_num));
                if (pbuf_copy_partial(p, content_len_num, content_len_num_len, content_len_hdr + 16) == content_len_num_len) {
                    int len = atoi(content_len_num);
                    if ((len >= 0) && ((u32_t)len < HTTPC_CONTENT_LEN_INVALID)) {
                        *content_length = (u32_t)len;
                    }
                }
            }
        }
        return ERR_OK;
    }
    return ERR_VAL;
}

/** http client tcp recv callback */
static err_t
httpc_tcp_recv(void* arg, struct altcp_pcb* pcb, struct pbuf* p, err_t r)
{
    httpc_state_t* req = (httpc_state_t*)arg;
    LWIP_UNUSED_ARG(r);

    if (p == NULL) {
        httpc_result_t result;
        if (req->parse_state != HTTPC_PARSE_RX_DATA) {
            /* did not get RX data yet */
            result = HTTPC_RESULT_ERR_CLOSED;
        }
        else if ((req->hdr_content_len != HTTPC_CONTENT_LEN_INVALID) &&
                 (req->hdr_content_len != req->rx_content_len)) {
            /* header has been received with content length but not all data received */
            result = HTTPC_RESULT_ERR_CONTENT_LEN;
        }
        else {
            /* receiving data and either all data received or no content length header */
            result = HTTPC_RESULT_OK;
        }
        return httpc_close(req, result, req->rx_status, ERR_OK);
    }
    if (req->parse_state != HTTPC_PARSE_RX_DATA) {
        if (req->rx_hdrs == NULL) {
            req->rx_hdrs = p;
        }
        else {
            pbuf_cat(req->rx_hdrs, p);
        }
        if (req->parse_state == HTTPC_PARSE_WAIT_FIRST_LINE) {
            u16_t status_str_off;
            err_t err = http_parse_response_status(req->rx_hdrs, &req->rx_http_version, &req->rx_status, &status_str_off);
            if (err == ERR_OK) {
                /* don't care status string */
                req->parse_state = HTTPC_PARSE_WAIT_HEADERS;
            }
        }
        if (req->parse_state == HTTPC_PARSE_WAIT_HEADERS) {
            u16_t total_header_len;
            err_t err = http_wait_headers(req->rx_hdrs, &req->hdr_content_len, &total_header_len);
            if (err == ERR_OK) {
                struct pbuf* q;
                /* full header received, send window update for header bytes and call into client callback */
                altcp_recved(pcb, total_header_len);
                if (req->conn_settings) {
                    if (req->conn_settings->headers_done_fn) {
                        err = req->conn_settings->headers_done_fn(req, req->callback_arg, req->rx_hdrs, total_header_len, req->hdr_content_len);
                        if (err != ERR_OK) {
                            return httpc_close(req, HTTPC_RESULT_LOCAL_ABORT, req->rx_status, err);
                        }
                    }
                }
                /* hide header bytes in pbuf */
                q = pbuf_free_header(req->rx_hdrs, total_header_len);
                p = q;
                req->rx_hdrs = NULL;
                /* go on with data */
                req->parse_state = HTTPC_PARSE_RX_DATA;
            }
        }
    }
    if ((p != NULL) && (req->parse_state == HTTPC_PARSE_RX_DATA)) {
        req->rx_content_len += p->tot_len;
        if (req->recv_fn != NULL) {
            /* directly return here: the connection migth already be aborted from the callback! */
            return req->recv_fn(req->callback_arg, pcb, p, r);
        }
        else {
            altcp_recved(pcb, p->tot_len);
            pbuf_free(p);
        }
    }
    return ERR_OK;
}

/** http client tcp err callback */
static void
httpc_tcp_err(void* arg, err_t err)
{
    httpc_state_t* req = (httpc_state_t*)arg;
    if (req != NULL) {
        /* pcb has already been deallocated */
        req->pcb = NULL;
        httpc_close(req, HTTPC_RESULT_ERR_CLOSED, 0, err);
    }
}

/** http client tcp poll callback */
static err_t
httpc_tcp_poll(void* arg, struct altcp_pcb* pcb)
{
    /* implement timeout */
    httpc_state_t* req = (httpc_state_t*)arg;
    LWIP_UNUSED_ARG(pcb);
    if (req != NULL) {
        if (req->timeout_ticks) {
            req->timeout_ticks--;
        }
        if (!req->timeout_ticks) {
            return httpc_close(req, HTTPC_RESULT_ERR_TIMEOUT, 0, ERR_OK);
        }
    }
    return ERR_OK;
}

/** http client tcp sent callback */
static err_t
httpc_tcp_sent(void* arg, struct altcp_pcb* pcb, u16_t len)
{
    /* nothing to do here for now */
    LWIP_UNUSED_ARG(arg);
    LWIP_UNUSED_ARG(pcb);
    LWIP_UNUSED_ARG(len);
    return ERR_OK;
}

/** http client tcp connected callback */
static err_t
httpc_tcp_connected(void* arg, struct altcp_pcb* pcb, err_t err)
{
    err_t r;
    httpc_state_t* req = (httpc_state_t*)arg;
    LWIP_UNUSED_ARG(pcb);
    LWIP_UNUSED_ARG(err);

    /* send request; last char is zero termination */
    r = altcp_write(req->pcb, req->request->payload, req->request->len - 1, TCP_WRITE_FLAG_COPY);
    if (r != ERR_OK) {
        /* could not write the single small request -> fail, don't retry */
        return httpc_close(req, HTTPC_RESULT_ERR_MEM, 0, r);
    }
    /* everything written, we can free the request */
    pbuf_free(req->request);
    req->request = NULL;

    altcp_output(req->pcb);
    return ERR_OK;
}

/** Start the http request when the server IP addr is known */
static err_t
httpc_get_internal_addr(httpc_state_t* req, const ip_addr_t* ipaddr)
{
    err_t err;
    LWIP_ASSERT("req != NULL", req != NULL);

    if (&req->remote_addr != ipaddr) {
        /* fill in remote addr if called externally */
        req->remote_addr = *ipaddr;
    }

    err = altcp_connect(req->pcb, &req->remote_addr, req->remote_port, httpc_tcp_connected);
    if (err == ERR_OK) {
        return ERR_OK;
    }
    LWIP_DEBUGF(HTTPC_DEBUG_WARN_STATE, ("tcp_connect failed: %d\n", (int)err));
    return err;
}

#if LWIP_DNS
/** DNS callback
 * If ipaddr is non-NULL, resolving succeeded and the request can be sent, otherwise it failed.
 */
static void
httpc_dns_found(const char* hostname, const ip_addr_t* ipaddr, void* arg)
{
    httpc_state_t* req = (httpc_state_t*)arg;
    err_t err;
    httpc_result_t result;

    LWIP_UNUSED_ARG(hostname);

    if (ipaddr != NULL) {
        err = httpc_get_internal_addr(req, ipaddr);
        if (err == ERR_OK) {
            return;
        }
        result = HTTPC_RESULT_ERR_CONNECT;
    }
    else {
        LWIP_DEBUGF(HTTPC_DEBUG_WARN_STATE, ("httpc_dns_found: failed to resolve hostname: %s\n",
                                             hostname));
        result = HTTPC_RESULT_ERR_HOSTNAME;
        err = ERR_ARG;
    }
    httpc_close(req, result, 0, err);
}
#endif /* LWIP_DNS */

/** Start the http request after converting 'server_name' to ip address (DNS or address string) */
static err_t
httpc_get_internal_dns(httpc_state_t* req, const char* server_name)
{
    err_t err;
    LWIP_ASSERT("req != NULL", req != NULL);

#if LWIP_DNS
    err = dns_gethostbyname(server_name, &req->remote_addr, httpc_dns_found, req);
#else
    err = ipaddr_aton(server_name, &req->remote_addr) ? ERR_OK : ERR_ARG;
#endif

    if (err == ERR_OK) {
        /* cached or IP-string */
        err = httpc_get_internal_addr(req, &req->remote_addr);
    }
    else if (err == ERR_INPROGRESS) {
        return ERR_OK;
    }
    return err;
}

static int
httpc_create_request_string(const httpc_connection_t* settings, const char* server_name, int server_port, const char* uri,
                            int use_host, char* buffer, size_t buffer_size)
{
    if (settings->use_proxy) {
        LWIP_ASSERT("server_name != NULL", server_name != NULL);
        if (server_port != HTTP_DEFAULT_PORT) {
            return snprintf(buffer, buffer_size, HTTPC_REQ_11_PROXY_PORT_FORMAT(server_name, server_port, uri, server_name));
        }
        else {
            return snprintf(buffer, buffer_size, HTTPC_REQ_11_PROXY_FORMAT(server_name, uri, server_name));
        }
    }
    else if (use_host) {
        LWIP_ASSERT("server_name != NULL", server_name != NULL);
        return snprintf(buffer, buffer_size, HTTPC_REQ_11_HOST_FORMAT(uri, server_name));
    }
    else {
        return snprintf(buffer, buffer_size, HTTPC_REQ_11_FORMAT(uri));
    }
}

/** Initialize the connection struct */
static err_t
httpc_init_connection_common(httpc_state_t** connection, const httpc_connection_t* settings, const char* server_name,
                             u16_t server_port, const char* uri, altcp_recv_fn recv_fn, void* callback_arg, int use_host)
{
    size_t alloc_len;
    mem_size_t mem_alloc_len;
    int req_len, req_len2;
    httpc_state_t* req;
#if HTTPC_DEBUG_REQUEST
    size_t server_name_len, uri_len;
#endif

    LWIP_ASSERT("uri != NULL", uri != NULL);

    /* get request len */
    req_len = httpc_create_request_string(settings, server_name, server_port, uri, use_host, NULL, 0);
    if ((req_len < 0) || (req_len > 0xFFFF)) {
        return ERR_VAL;
    }
    /* alloc state and request in one block */
    alloc_len = sizeof(httpc_state_t);
#if HTTPC_DEBUG_REQUEST
    server_name_len = server_name ? strlen(server_name) : 0;
    uri_len = strlen(uri);
    alloc_len += server_name_len + 1 + uri_len + 1;
#endif
    mem_alloc_len = (mem_size_t)alloc_len;
    if ((mem_alloc_len < alloc_len) || (req_len + 1 > 0xFFFF)) {
        return ERR_VAL;
    }

    req = (httpc_state_t*)mem_malloc((mem_size_t)alloc_len);
    if(req == NULL) {
        return ERR_MEM;
    }
    memset(req, 0, sizeof(httpc_state_t));
    req->timeout_ticks = HTTPC_POLL_TIMEOUT;
    req->request = pbuf_alloc(PBUF_RAW, (u16_t)(req_len + 1), PBUF_RAM);
    if (req->request == NULL) {
        httpc_free_state(req);
        return ERR_MEM;
    }
    if (req->request->next != NULL) {
        /* need a pbuf in one piece */
        httpc_free_state(req);
        return ERR_MEM;
    }
    req->hdr_content_len = HTTPC_CONTENT_LEN_INVALID;
#if HTTPC_DEBUG_REQUEST
    req->server_name = (char*)(req + 1);
    if (server_name) {
        memcpy(req->server_name, server_name, server_name_len + 1);
    }
    req->uri = req->server_name + server_name_len + 1;
    memcpy(req->uri, uri, uri_len + 1);
#endif
    req->pcb = altcp_new(settings->altcp_allocator);
    if(req->pcb == NULL) {
        httpc_free_state(req);
        return ERR_MEM;
    }
    req->remote_port = settings->use_proxy ? settings->proxy_port : server_port;
    altcp_arg(req->pcb, req);
    altcp_recv(req->pcb, httpc_tcp_recv);
    altcp_err(req->pcb, httpc_tcp_err);
    altcp_poll(req->pcb, httpc_tcp_poll, HTTPC_POLL_INTERVAL);
    altcp_sent(req->pcb, httpc_tcp_sent);

    /* set up request buffer */
    req_len2 = httpc_create_request_string(settings, server_name, server_port, uri, use_host,
                                           (char*)req->request->payload, req_len + 1);
    if (req_len2 != req_len) {
        httpc_free_state(req);
        return ERR_VAL;
    }

    req->recv_fn = recv_fn;
    req->conn_settings = settings;
    req->callback_arg = callback_arg;

    *connection = req;
    return ERR_OK;
}

/**
 * Initialize the connection struct
 */
static err_t
httpc_init_connection(httpc_state_t** connection, const httpc_connection_t* settings, const char* server_name,
                      u16_t server_port, const char* uri, altcp_recv_fn recv_fn, void* callback_arg)
{
    return httpc_init_connection_common(connection, settings, server_name, server_port, uri, recv_fn, callback_arg, 1);
}


/**
 * Initialize the connection struct (from IP address)
 */
static err_t
httpc_init_connection_addr(httpc_state_t** connection, const httpc_connection_t* settings,
                           const ip_addr_t* server_addr, u16_t server_port, const char* uri,
                           altcp_recv_fn recv_fn, void* callback_arg)
{
    char* server_addr_str = ipaddr_ntoa(server_addr);
    if (server_addr_str == NULL) {
        return ERR_VAL;
    }
    return httpc_init_connection_common(connection, settings, server_addr_str, server_port, uri,
                                        recv_fn, callback_arg, 1);
}

/**
 * @ingroup httpc
 * HTTP client API: get a file by passing server IP address
 *
 * @param server_addr IP address of the server to connect
 * @param port tcp port of the server
 * @param uri uri to get from the server, remember leading "/"!
 * @param settings connection settings (callbacks, proxy, etc.)
 * @param recv_fn the http body (not the headers) are passed to this callback
 * @param callback_arg argument passed to all the callbacks
 * @param connection retreives the connection handle (to match in callbacks)
 * @return ERR_OK if starting the request succeeds (callback_fn will be called later)
 *         or an error code
 */
err_t
httpc_get_file(const ip_addr_t* server_addr, u16_t port, const char* uri, const httpc_connection_t* settings,
               altcp_recv_fn recv_fn, void* callback_arg, httpc_state_t** connection)
{
    err_t err;
    httpc_state_t* req;

    LWIP_ERROR("invalid parameters", (server_addr != NULL) && (uri != NULL) && (recv_fn != NULL), return ERR_ARG;);

    err = httpc_init_connection_addr(&req, settings, server_addr, port,
                                     uri, recv_fn, callback_arg);
    if (err != ERR_OK) {
        return err;
    }

    if (settings->use_proxy) {
        err = httpc_get_internal_addr(req, &settings->proxy_addr);
    }
    else {
        err = httpc_get_internal_addr(req, server_addr);
    }
    if(err != ERR_OK) {
        httpc_free_state(req);
        return err;
    }

    if (connection != NULL) {
        *connection = req;
    }
    return ERR_OK;
}

/**
 * @ingroup httpc
 * HTTP client API: get a file by passing server name as string (DNS name or IP address string)
 *
 * @param server_name server name as string (DNS name or IP address string)
 * @param port tcp port of the server
 * @param uri uri to get from the server, remember leading "/"!
 * @param settings connection settings (callbacks, proxy, etc.)
 * @param recv_fn the http body (not the headers) are passed to this callback
 * @param callback_arg argument passed to all the callbacks
 * @param connection retreives the connection handle (to match in callbacks)
 * @return ERR_OK if starting the request succeeds (callback_fn will be called later)
 *         or an error code
 */
err_t
httpc_get_file_dns(const char* server_name, u16_t port, const char* uri, const httpc_connection_t* settings,
                   altcp_recv_fn recv_fn, void* callback_arg, httpc_state_t** connection)
{
    err_t err;
    httpc_state_t* req;

    LWIP_ERROR("invalid parameters", (server_name != NULL) && (uri != NULL) && (recv_fn != NULL), return ERR_ARG;);

    err = httpc_init_connection(&req, settings, server_name, port, uri, recv_fn, callback_arg);
    if (err != ERR_OK) {
        return err;
    }

    if (settings->use_proxy) {
        err = httpc_get_internal_addr(req, &settings->proxy_addr);
    }
    else {
        err = httpc_get_internal_dns(req, server_name);
    }
    if(err != ERR_OK) {
        httpc_free_state(req);
        return err;
    }

    if (connection != NULL) {
        *connection = req;
    }
    return ERR_OK;
}

#if LWIP_HTTPC_HAVE_FILE_IO
/* Implementation to disk via fopen/fwrite/fclose follows */

typedef struct _httpc_filestate {
    const char* local_file_name;
    FILE* file;
    httpc_connection_t settings;
    const httpc_connection_t* client_settings;
    void* callback_arg;
} httpc_filestate_t;

static void httpc_fs_result(void* arg, httpc_result_t httpc_result, u32_t rx_content_len,
                            u32_t srv_res, err_t err);

/** Initalize http client state for download to file system */
static err_t
httpc_fs_init(httpc_filestate_t** filestate_out, const char* local_file_name,
              const httpc_connection_t* settings, void* callback_arg)
{
    httpc_filestate_t* filestate;
    size_t file_len, alloc_len;
    FILE* f;

    file_len = strlen(local_file_name);
    alloc_len = sizeof(httpc_filestate_t) + file_len + 1;

    filestate = (httpc_filestate_t*)mem_malloc((mem_size_t)alloc_len);
    if (filestate == NULL) {
        return ERR_MEM;
    }
    memset(filestate, 0, sizeof(httpc_filestate_t));
    filestate->local_file_name = (const char*)(filestate + 1);
    memcpy((char*)(filestate + 1), local_file_name, file_len + 1);
    filestate->file = NULL;
    filestate->client_settings = settings;
    filestate->callback_arg = callback_arg;
    /* copy client settings but override result callback */
    memcpy(&filestate->settings, settings, sizeof(httpc_connection_t));
    filestate->settings.result_fn = httpc_fs_result;

    f = fopen(local_file_name, "wb");
    if(f == NULL) {
        /* could not open file */
        mem_free(filestate);
        return ERR_VAL;
    }
    filestate->file = f;
    *filestate_out = filestate;
    return ERR_OK;
}

/** Free http client state for download to file system */
static void
httpc_fs_free(httpc_filestate_t* filestate)
{
    if (filestate != NULL) {
        if (filestate->file != NULL) {
            fclose(filestate->file);
            filestate->file = NULL;
        }
        mem_free(filestate);
    }
}

/** Connection closed (success or error) */
static void
httpc_fs_result(void* arg, httpc_result_t httpc_result, u32_t rx_content_len,
                u32_t srv_res, err_t err)
{
    httpc_filestate_t* filestate = (httpc_filestate_t*)arg;
    if (filestate != NULL) {
        if (filestate->client_settings->result_fn != NULL) {
            filestate->client_settings->result_fn(filestate->callback_arg, httpc_result, rx_content_len,
                                                  srv_res, err);
        }
        httpc_fs_free(filestate);
    }
}

/** tcp recv callback */
static err_t
httpc_fs_tcp_recv(void* arg, struct altcp_pcb* pcb, struct pbuf* p, err_t err)
{
    httpc_filestate_t* filestate = (httpc_filestate_t*)arg;
    struct pbuf* q;
    LWIP_UNUSED_ARG(err);

    LWIP_ASSERT("p != NULL", p != NULL);

    for (q = p; q != NULL; q = q->next) {
        fwrite(q->payload, 1, q->len, filestate->file);
    }
    altcp_recved(pcb, p->tot_len);
    pbuf_free(p);
    return ERR_OK;
}

/**
 * @ingroup httpc
 * HTTP client API: get a file to disk by passing server IP address
 *
 * @param server_addr IP address of the server to connect
 * @param port tcp port of the server
 * @param uri uri to get from the server, remember leading "/"!
 * @param settings connection settings (callbacks, proxy, etc.)
 * @param callback_arg argument passed to all the callbacks
 * @param connection retreives the connection handle (to match in callbacks)
 * @return ERR_OK if starting the request succeeds (callback_fn will be called later)
 *         or an error code
 */
err_t
httpc_get_file_to_disk(const ip_addr_t* server_addr, u16_t port, const char* uri, const httpc_connection_t* settings,
                       void* callback_arg, const char* local_file_name, httpc_state_t** connection)
{
    err_t err;
    httpc_state_t* req;
    httpc_filestate_t* filestate;

    LWIP_ERROR("invalid parameters", (server_addr != NULL) && (uri != NULL) && (local_file_name != NULL), return ERR_ARG;);

    err = httpc_fs_init(&filestate, local_file_name, settings, callback_arg);
    if (err != ERR_OK) {
        return err;
    }

    err = httpc_init_connection_addr(&req, &filestate->settings, server_addr, port,
                                     uri, httpc_fs_tcp_recv, filestate);
    if (err != ERR_OK) {
        httpc_fs_free(filestate);
        return err;
    }

    if (settings->use_proxy) {
        err = httpc_get_internal_addr(req, &settings->proxy_addr);
    }
    else {
        err = httpc_get_internal_addr(req, server_addr);
    }
    if(err != ERR_OK) {
        httpc_fs_free(filestate);
        httpc_free_state(req);
        return err;
    }

    if (connection != NULL) {
        *connection = req;
    }
    return ERR_OK;
}

/**
 * @ingroup httpc
 * HTTP client API: get a file to disk by passing server name as string (DNS name or IP address string)
 *
 * @param server_name server name as string (DNS name or IP address string)
 * @param port tcp port of the server
 * @param uri uri to get from the server, remember leading "/"!
 * @param settings connection settings (callbacks, proxy, etc.)
 * @param callback_arg argument passed to all the callbacks
 * @param connection retreives the connection handle (to match in callbacks)
 * @return ERR_OK if starting the request succeeds (callback_fn will be called later)
 *         or an error code
 */
err_t
httpc_get_file_dns_to_disk(const char* server_name, u16_t port, const char* uri, const httpc_connection_t* settings,
                           void* callback_arg, const char* local_file_name, httpc_state_t** connection)
{
    err_t err;
    httpc_state_t* req;
    httpc_filestate_t* filestate;

    LWIP_ERROR("invalid parameters", (server_name != NULL) && (uri != NULL) && (local_file_name != NULL), return ERR_ARG;);

    err = httpc_fs_init(&filestate, local_file_name, settings, callback_arg);
    if (err != ERR_OK) {
        return err;
    }

    err = httpc_init_connection(&req, &filestate->settings, server_name, port,
                                uri, httpc_fs_tcp_recv, filestate);
    if (err != ERR_OK) {
        httpc_fs_free(filestate);
        return err;
    }

    if (settings->use_proxy) {
        err = httpc_get_internal_addr(req, &settings->proxy_addr);
    }
    else {
        err = httpc_get_internal_dns(req, server_name);
    }
    if(err != ERR_OK) {
        httpc_fs_free(filestate);
        httpc_free_state(req);
        return err;
    }

    if (connection != NULL) {
        *connection = req;
    }
    return ERR_OK;
}
#endif /* LWIP_HTTPC_HAVE_FILE_IO */

#endif /* LWIP_TCP && LWIP_CALLBACK_API */
